AC-Coupling vs. DC-Coupling
The system design connecting a battery to solar panels; DC systems use a shared hybrid inverter, while AC systems use separate battery inverters.
AC-coupling and DC-coupling describe the two fundamental electrical connection layouts for pairing residential solar panels with energy storage.
In a DC-coupled system, solar panels and battery storage connect to a single central hybrid inverter (e.g. Tesla Powerwall 3). Power flows from panels directly to the battery with 0 conversion steps, achieving high 90%+ round-trip efficiency.
In an AC-coupled system, the solar panels and battery bank have independent inverters (e.g. Enphase IQ Battery 5P). Power converts from DC to AC and back to DC to enter the battery. While AC systems incur ~4% more conversion losses, they connect directly to any AC breaker panel, making retrofits on existing solar arrays fast and inexpensive.
Why it matters
DC-coupling is premier for new solar installations, while AC-coupling is ideal for retrofitting storage onto pre-existing solar arrays.
Example
Adding an AC-coupled battery to a 5-year-old solar roof allows you to keep your existing solar inverter without paying for costly rewiring.